This project is designed to determine the effect of myocardial infarction and shock upon cardiac functon and the effect of therapy directed at the systemic circulation upon the damaged myocardium. A closed chest model for myocardial infarction with sized plastic microspheres will be utilized to produce cardiogenic shock in dogs. The therapy used will consist of vasopressor drugs, vasodilator drugs, and epinephrine tolerance. High fidelity recordings of left ventricular pressure will be obtained with a catheter tip pressure transducer. Additionally, right and left atrial pressures will be monitored. In open chest dogs electromagnetic flow probes will be placed around the root of the aorta and both right and left coronary arteries. In addition a cannula will be placed in the coronary sinus through the right atrium for blood withdrawal. Cardiac pump performance will be evaluated by the following: Left ventricular end diastolic pressure, cardiac output, stroke volume, mean systolic ejection rate, and left ventricular minute work. Cardiac muscle performance will be evaluated by: Peak rate of ventricular pressure rise (peak DP/DT), time to peak dp/dt (t - dp/dt), and maximum velocity of contractile element shortening (Vmax). Myocardial metabolism will be studied by determining coronary flow, myocardial oxygen consumption, myocardial lactate and pyruvate consumption, lysosomal enzyme production and myocardial ATP. These studies wll be done in closed chest dogs during the first 18 months and in open chest dogs during the second 18 months of the research. The data will be analyzed using standard tests of statistical significance.